How to use signed bitconcat and bitsliceget?

Hello,

i am using Matlab for my Bachelor and i have got a problem with bitconcat and bitslice. If i concat or slice fi objects they are automatically unsigned. Does anyone know how to use bitconcat or bitslice signed?

All = bitconcat(fi(-100,1,16,0),fi(5,1,16,0));

y1 = bitsliceget(cast_to_fi(All),16,1);

y2 = bitsliceget(cast_to_fi(All),32,17);

y1 =

5

DataTypeMode: Fixed-point: binary point scaling

Signedness: Unsigned

WordLength: 16

FractionLength: 0

y2 =

65436

DataTypeMode: Fixed-point: binary point scaling

Signedness: Unsigned

WordLength: 16

FractionLength: 0

I do not know how to solve this. i need y2 = -100 there. Is there any way to use bitconcat/bitslice signed? Or any way to solve this problem.

Yours sincerely

Mustafa

[Slava Razumov]

https://www.mathworks.com/matlabcentral/answers/226225-keep-sign-when-using-bitsliceget

Answer 1

[Kiran Kintali]

The bitwise operator functions such as bitsliceget and bitconcat operate on underlying stored integer bits.

Once bitwise operations of slice/concat are performed, you should be able to update the result using reinterpretcast function to the proper type of your choice to see the underlying real world value.

https://www.mathworks.com/help/fixedpoint/ref/reinterpretcast.html

>> T = numerictype(1,16,0);
>> A = bitconcat(fi(-100, T), fi(5, T));
>> y1 = bitsliceget(A, 16, 1);
>> y2 = bitsliceget(A, 32, 17);
>> y1_rwv = reinterpretcast(y1, T);
>> y2_rwv = reinterpretcast(y2, T);
>> y1_rwv, y2_rwv

y1_rwv = 

     5

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 0

y2_rwv = 

  -100

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 0
>>